P11 & P22 Hardness Issue

Date 09-08-2010 16:35

We are facing one serious concern regarding PWHT of weld joints of A335 Grade P11 & P22 piping in very high pressure superheated steam and syn gas service. Due to some unforeseen circumstances at our site, PWHT of some weld joints was not done effectively and resulted in higher hardness of weld joints although HAZ area hardness values are OK. The hardness number of weld joints is in the range of 260 - 320 HB which is unacceptable as per code requirements.

I want to seek your expert opinion on the following:

1. Can we take these weld joints is operation and defer PWHT for planned Outage after one and a half year from now?

2. Is there any relaxation which can be taken in hardness readings, for example, welds with hardness up to 260 may be accepted and above this number must be PWHT again?

3. What effects can it cause after taking these weld joints in service? Weld failure can occur immediately or would take some time?

4. As HAZ area hardness number is standing in the range of 115 - 150, would repeating PWHT effect this number and further reduce the hardness of HAZ which may not be acceptable?

Your inputs would definitely help me in making a correct decision.

Regards,

Ashfaq

By 3.2 Inspector (***)

Date 09-09-2010 08:11 Edited 09-09-2010 13:14

Let me understand....
The weld itself has a hardness of 260 - 320 and the HAZ only 115 - 150 (seems very very low), is that corrct? Which unit is the hardness meassured in?

The thickness of the pipe would also be good to know.

Has the correct filler material been used?

3.2

EDIT: I now see it is in HB :)

By js55

Date 09-09-2010 12:46

3.2 has good questions I didn't consider in the other thread.
These numbers do seem odd.
The spread of numbers seems to be excessive as well. If your using a unit such as the MIC 10 try a telebrineller, or something with a larger representative sample area. It will homogenize the microstructure better and give a more consistent response.